function ajax() {
    var xhr = new XMLHttpRequest()
    xhr.open("GET", "./js/dati.json")
    xhr.send()
    xhr.onreadystatechange = function () {
        if (xhr.status == 200 && xhr.readyState == 4) {
            var timuList = JSON.parse(xhr.response)
            // console.log(timuList)
            var randomNum = parseInt(Math.random() * timuList.length)
            // console.log(timuList)
            var del = timuList.splice(randomNum, 1);
            console.log(del[0])
            currentTimu = del[0]
            timu.innerHTML = `
                        <h2 class="timu">题目：${del[0].quiz}</h2>
                    `
            main.innerHTML = `
                    <div class="optionItem" data-index="1">
                    A:${del[0].options[0]}
                </div>
                <div class="optionItem" data-index="2">
                    B:${del[0].options[1]}
                </div>
                <div class="optionItem " data-index="3">
                    C:${del[0].options[2]}
                </div>
                <div class="optionItem " data-index="4">
                    D:${del[0].options[3]}
                </div>
                    `
        }
    }
}